The present invention relates generally to simulating muting in a drive control device for a striking member in a sound generation mechanism. For example, the present invention relates to auto-playing musical instruments provided with an automatic performance function, such as pianos, celestas and glockenspiels, and more particularly to drive control of a striking member, such as a hammer, provided in an auto-playing musical instrument.
Auto-playing pianos have been known as an example of acoustic musical instruments that execute an automatic performance in accordance with performance instructing data. Generally; auto-playing pianos include a drive mechanism that drives hammers provided in an ordinary piano, and a control device that controls driving, by the drive mechanism, of the hammers. The control device of the auto-playing piano controls behavior of the drive mechanism to drive the hammers, provided in corresponding relation to strings (more specifically, sets of stings), in accordance with performance instruction data indicative of pitches of strings (sets of strings) that should be struck by the hammers and string striking timing and intensity. As a consequence, a music piece is automatically performed or played by the auto-playing piano.
Some musical instruments, such as pianos, having sounding members (strings in the case of pianos) each of which can vibrate by being struck by a corresponding one of the hammers to thereby generate a particular sound (or tone), are provided with a muting mechanism. For example, many of the pianos include a soft pedal mechanism as the muting mechanism. Normally; in the muting mechanism of a grand-type piano, an entire hammer mechanism is caused to shift rightward relative to the strings in response to a human player depressing the soft pedal. Thus, some persons skilled in the art may call the muting mechanism a “shift pedal”. Thus, for convenience of description in this specification, the muting mechanism (including the mechanism called “shift pedal mechanism”) provided in the piano will hereinafter be referred to as “soft pedal mechanism”, and a pedal provided in the soft pedal mechanism will hereinafter be referred to as “soft pedal”.
In the case of a grand-type piano, once a key is struck or depressed with the soft pedal of the soft pedal mechanism depressed, the set of strings (one or more strings) corresponding to the depressed key is struck by the corresponding hammer with the position of the hammer displaced perpendicularly to a direction in which the strings extend (i.e., string-extending direction). Due to such displacement of the hammer, the number of the strings struck by the one hammer decreases, or a position of the hammer striking the strings shifts toward an end of the strings (more specifically, an end of the set of strings), as compared to a case where the key is struck or depressed with the soft pedal not depressed. Thus, generally, a sound audibly generated from the piano with the soft pedal depressed will give a listener a softer impression.
Further, in the case of an uptight-type piano, once a key is struck or depressed with the soft pedal of the soft pedal mechanism depressed, the corresponding strings are struck by the hammer whose pivoting movement is started at a position closer to the strings than normal. Thus, in this case, the hammer strikes the strings at a low velocity as compared to a case where the strings are struck by the hammer with the soft pedal not depressed. As a consequence, a sound of a smaller volume will be generated from the piano.
There has also been known a technique for executing an automatic perfomiance of a music piece, involving muting, in accordance with performance instruction data including data (muting data) indicative of present/absence or depths of depression of the soft pedal. For example, in an auto-playing piano disclosed in Japanese Patent Application Laid-open Publication No. HE-5-289657 (hereinafter referred to as “Patent Literature 1”), if soft pedal event information, indicating presence/absence of depression of the soft pedal at the time of generation of an ON event instructing striking of a key, is indicative of “ON”, then conversion of key striking intensity information is executed, so that the key is driven in accordance with the converted key striking intensity information. As a result, an automatic performance imparted with a muting effect is executed without the soft pedal mechanism being driven.
In the case of the auto-playing piano disclosed in Patent Literature 1, if muting is instructed by the muting data when striking of a key has been instructed by the performance instruction data, an average electric power to be input to a corresponding key solenoid, which drives the hammer via the key, is reduced by conversion of the key striking intensity information. As a consequence, a string striking velocity of the hammer decreases so that a weak sound is generated from the corresponding strings, as compared to a case where conversion of the key striking intensity information is not executed.
If muting has been executed by merely converting the key striking intensity information to thereby reduce hammer driving force, a moving velocity of the hammer decreases without drive start timing of the hammer being changed, so that timing at which the hammer strikes the corresponding strings (string striking timing) would get delayed. FIG. 9 is a graph showing how the string striking timing is displaced when muting has been executed by mere conversion of the key striking intensity information. In FIG. 9, the horizontal axis represents elapsed times from start timing of key depression by the key solenoid, while the vertical axis represents depths of the key depression. As the key is depressed by the key solenoid, the hammer contacting the depressed key is driven to move toward the corresponding strings. Therefore, the depth of the key depression is proportional to a distance between the hammer and the strings.
In FIG. 9, (a) shows variation over time of the depth of the key depression from the key depression start time to the string striking time in a case where muting is not executed, and (b) shows variation over time of the depth of the key depression from the key depression start timing to the string striking timing in a case where muting is executed. As shown by these graph curves, string striking timing T2 in the case where muting is executed would lag behind string striking timing T1 in the case where muting is not executed.